Gas-phase formation of mono- and dications from iron-subgroup decamethylmetallocenes and their calculation by the density functional method

The possibility of forming mono- [C5Me5MC5Me4CH2]+ (1) and dications [1,2(CH2)2C5Me3MC5Me5]2+ (2) and 1,1′-[M(C5Me4CH2)2]2+ (3) starting from iron subgroup decamethylmetallocenes (Fe (a), Ru (b), Os (c)) was studied using electron-impact mass-spectrometry. The peaks of both single (M+) and doubly charged (M2+) molecular ions are present in the mass-spectra of all compounds studied. The basic fragmentation patterns are the elimination of one (M+) and two atoms of hydrogen (M2+) to give the corresponding mono- (1) and dications (2 and/or 3). The density-functional method was used for ab initio calculations of the geometry and total energies of cations 1 and 2 and the anti, syn, and gauche conformers of 3 for comparison with the dication [1,3-(CH2)2C5Me3MC5Me5]2+ (2b′). The calculation data for monocations 1a–c are in a good agreement with the results of X-ray analysis of these cations except for the MCH2 interatomic distances and angles α, which are presumed to be most sensitive to phase changes. The relative order of stabilities of the mono- and dications was as follows: F